The University of Michigan Solar Car Team car competes during the first day of the 2015 World Solar Challenge near Katherine, Australia, on Sunday. The race features 45 solar cars from 25 different countries in a 3,000 km race from Darwin to Adelaide.

A Dutch car overtakes a competitor going 81 miles per hour through the blazing Australian outback, then resumes cruising speed at 56 m.p.h., finishing the 1,800 mile race first – all without using a gallon of gas.

The solar car race in Australia on Thursday, which a vehicle from Delft University won for the second consecutive time, displays the upper limits of solar power, and researchers are challenged to develop a working car that could lead to a consumer model.

The main rule of the World Solar Challenge, a race for about 50 cars occurring every two years since 1987, is that cars must use the sun for power, the BBC reported. Cars may store only 5 kilowatts of energy – by contrast, a single light bulb on for 10 hours a day uses about 4 kilowatts a week, according to Forbes. Each car must take the rest of its power from the sun or from the motion of the car itself.

"(Distilled water) is used to spray over solar arrays at control stops to keep the temperature down (and consequently: to maximize the output)," Michael Van Baal, the winning team's spokesman, wrote on the Nuon Solar Team blog. "Finding demi-water in October is pretty hopeless, as all top teams need it, so you better stock up early."

The distilled water is better than tap water, which leaves a layer of salt on the solar panels as it evaporates.

"The past decade has been a remarkable time for the solar industry. Last year up to a third of all new generation capacity in the US was solar," Francis O’Sullivan, director of research and analysis at MIT’s Energy Initiative, told The Christian Science Monitor. "However, continued rapid growth in solar is not an inevitability."

"Despite the Tesla announcement, we’re not there yet," said Richard Schmalensee, chairman of an MIT Future of Solar Energy study, according to The Christian Science Monitor. "We’re not close to being there yet."

Working with solar power continues to require a full measure of flexibility. The World Solar Challenge started Sunday in Darwin, Australia, and ended Thursday in Adelaide, the BBC reported.

Temperatures reached 111 degrees Fahrenheit, and the racers did not want to use an ounce of their sun-produced energy on air-conditioning. The drivers exercised and trained in heat rooms beforehand to prepare. But during the race itself, their best ally was water, UPI News reported. The Delft University team even put a hole in the car itself to drain out the sweat the drivers generated under the blazing sun.